The enzymatic method is based on the determination of sarcosine from creatinine with the aid of creatininase, creatinase, and sarcosine oxidase. The liberated hydrogen peroxide is measured via a modified Trinder reaction using a colorimetric indicator. Optimization of the buffer system and the colorimetric indicator enables the creatinine concentration to be quantified both precisely and specifically.(Package insert: Roche Cobas creatinine reagent, Roche Diagnostics, Indianapolis IN, August 2007)

Estimated Glomerular Filtration Rate (eGFR):

Serum creatinine is determined by an enzymatic colorimetric assay calibrated to an isotope dilution mass spectrometry (IDMS)-traceable method. The eGFR value is calculated from serum creatinine using the IDMS-traceable Modification of Diet in Renal Disease (MDRD) Study equation.(2) When creatinine is in mg/dL (conventional units) this equation is: